1. Field of the Invention
The present invention relates to a method of fabricating a photomask, and more particularly, to a method of fabricating a microscopic hole photomask, in which line width patterning is appropriately compensated by a supplementary pattern and by which a precise line width can be provided.
2. Discussion of the Related Art
Generally, a photomask pattern directly affects a precision of a real pattern formed on a semiconductor substrate. If an optical proximity effect of the photomask pattern fails to be correctly taken into consideration, a pattern line width is distorted, unlike the intended exposure of a photolithography process. Hence, line width linearity is shortened to degrade semiconductor device characteristics.
In a method of fabricating a microscopic photomask according to a related art, even if design line widths, as shown in FIG. 1, are equal to each other regardless of a density of contact hole patterns, the optical proximity effect showing a light interference difference due to exposure intensity occurs in a real exposure, as shown in FIG. 2. Specifically, the difference in resolution is severe for a particular hole or holes in a contact hole mask. For instance, a hole 1B in a dense area of a mask is formed with greater proximity to adjacent holes than a more isolated hole, such as hole 1A which is formed in a sparse area. Hence, the quality of a hole that can be made in photoresist for hole A in the sparse area considerably differs (in a negative way) from a hole B formed in a more dense area in resolution.
However, since the related art method needs a supplementary pattern for controlling the optical proximity effect to overcome such a problem, time is wasted in fabricating the photomask and the number of the supplementary patterns increases in the photomask. Hence, the precision of the photomask pattern is lowered and is not able to yield precise critical dimensions.